The present invention has as object a flexible hose, particularly but not exclusively of the gardening type, provided with an inner mesh reinforcement structure. The invention also has as object a process for manufacturing such a reinforced hose.
Flexible gardening hoses are generally composed of an inner tubular layer and an external tubular layer made of polymer material, not necessarily of the same type.
Usually interposed between the two layers are one or more reinforcement layers configured as a function of the mechanical characteristics to be conferred to the hose, such as the resistance to bursting, the flexibility or the capacity to avoid the kinking phenomenon, i.e. the tendency of the hoses to be crushed when subjected to twisting with formation of a localized narrowing or obstruction.
The reinforcement layers are generally constituted by a textile, synthetic or natural fiber, wired or knitted with chain mesh of tricot type.
The reinforcement layer of wired type, if on one hand it ensures a limited expansion of the hose under pressure and is relatively simple and economical to produce, on the other hand has low resistance to kinking.
The reinforced layer of knitted type, while being more difficult and costly to make than the wired type, with respect to the latter resists much better to kinking, and hence is preferred in the case of medium-high level gardening hoses.
Nevertheless, the hose with knitted reinforcement is quite sensitive to variations of the internal pressure and reacts to the same by axially rotating, creating a number of difficulties in the case of use of hose-carrier trolleys and similar supports.
In order to overcome these drawbacks, gardening hoses have been made—one of which described in EP0623776—in which the knitted layer is formed by mesh wales and courses that are inclined with respect to the axis of the hose with opposite inclined angles.
Also in this case, however, there are non-negligible rotations under pressure, above all due to length or diameter variations of the hose which alter its geometry.
From FR2849148, an irrigation hose is known which is provided with two knitted reinforcement layers superimposed on each other and having mesh wales inclined with respect to the axis of the hose and mesh courses formed by parallel chains or meshes. The mesh courses of one of the layers are angularly spaced with respect to the mesh courses of the other layer in a manner so as to define a regular alternation of the mesh courses of the two knitted layers.
However, this solution has not proven to be satisfactory, since it is very difficult to achieve, and also has the drawback of defining overly wide spaces between the meshes, with consequent localized reduction of the resistance to bursting.
A further solution of hose with knitted reinforcement is known from U.S. Pat. No. 3,578,028, in which the reinforcement knitting is defined by mesh chains mutually intertwined in such a manner that the respective chain eyelets are partially superimposed on each other.
Nevertheless, also in this case the particular distribution of the mesh courses determines the presence of relatively wide empty spaces between the courses, spaces which represent clear points of lower resistance to the pressure.
In U.S. Pat. No. 3,201,954, a flexible hose is described having a reinforcement mesh formed by a spiraled portion and by a knitted portion.
The latter has chain eyelets distributed along mesh courses substantially parallel to the extension axis of the hose. In particular, each course has a plurality of slotted longitudinal eyelets in frontal contact with corresponding transverse sections.
Such solution has also not proven to be satisfactory, since it requires the presence of a large amount of yarn. In addition, it has poor resistance to kinking and twisting in the presence of high pressures, since the mesh wales defined by the different series of yarns have the same inclination angle.